2V Power Curve / Tradeoffs

DBMSTNG · May 31, 2004

XtorT'r said:
Man, this post got kinda nasty.

it happens from time to time when someone just won't shut up and admit they don't have a freakin clue.

kirkyg · May 31, 2004

Ben99GT said:
Go ahead, overlap the curves of a '96-'98 4V and a '99+ 2V, same mods or stock for stock. The 2V, on average, will make more peak torque and make more horsepower and torque below 3,000 rpm.

The Mach 1 4V is the only real exception to the 4V being weak down low.

The only 4v from 99 or newer that wouldn't put out more low end and high end power throughout the power curve is the 99+ pre-fix with choked off intake and exhaust manifolds. Again, hop in the seat of any 4valve and drive it and then open your mouth...your words would certainly be different.

kirkyg

Ben99GT · May 31, 2004

kirkyg said:
The only 4v from 99 or newer that wouldn't put out more low end and high end power throughout the power curve is the 99+ pre-fix with choked off intake and exhaust manifolds. Again, hop in the seat of any 4valve and drive it and then open your mouth...your words would certainly be different.

kirkyg

I have driven several '96-'98 Cobras, a couple '99 Cobras, an '01 Cobra, and a couple of Mach 1's.

I stand by my previous statement. 2V's are stronger down low than 4V's, the Mach 1 being the exception.

mogs01gt · May 31, 2004

well you guys are missing a lot of important parts.

4.6s have a very short stroke, that isnt that great for torque but it allows us to rev up higher and shift at a much higher RPM. My car makes power passed 6k with the heads and cams. No problem at all reving.

A lot is with our stock cams. They are a torquey cam to go along with the long runners of the intake. Since our cars have long runners, exhaust heavy cams and with the combination of the little stroke, this is why our cars seem a little different compared too the longer stroke and much longer bore of a ls1. These motors are pretty much in a league of their own.

ls1's are totally different than any other small block ever made. The heads alone will confuse the **** out of you. It is pretty much a perfect/best small block ever because of all the design and research put into the motor. The heads look like nascar heads.

kirkyg · May 31, 2004

Who brought ls1's into the mix? I thought we were discussing the SOHC vs DOHC?

Here's some facts for ya:

SOHC dyno:
http://dynoperformance.com/search_details.php?ID=699

DOHC dyno:
http://dynoperformance.com/search_details.php?ID=675

Both stock dynojets for respective engines...

Look at torque between 1850-2200 its higher for the 4valve and the 2valve dies when it gets over about 5500 rpms.

kirkyg

dkshadow · May 31, 2004

Usually a motor with a power peak at 5250 RPM would not exhibit the bias toward torque that the 260HP motor does. For example, the most common version of the LS1 reaches its torque and power peaks at 4000 RPM and 5200 RPM, respectively, almost exactly like the 260HP motor. But the power peak is 310HP and the torque peak is 340LB/FT. The numbers are closer to each other (30) than the Ford's numbers are (42).

There is another issue I have with the LS1... it seems like a smaller, OHC motor should come closer to the LS1 in power, not torque. That big LS1 should excel at torque and the OHC 4.6L should (to some extent) make it up on the top end. This is the stereotype. But the exact opposite is true... the torque peak of the 260HP motor is really pretty close to the LS1 (302 vs. 340) but the power differential is greater (260 vs. 305). In a race, the GT will do a decent job keeping up off-the-line and up to 60MPH, but the Z28 will absolutely run away on the top end. This seems backwards to me.

Its in the first post of this thread.

CuddaWuddaShuda · Jun 1, 2004

DBMSTANG: I get it. You interpret "bias toward torque" to mean that the FT/LB number is higher than the HP number. I can see where that interpretation would make me look dumb. But it's a stupid interpretation of the term "bias toward torque." It's an interpretation based on a comparison of two measurements despite the fact that they don't share the same units.

An engineer ought to know that comparing numbers with different units is not meaningful. Saying a motor has a torque bias because it has more FT/LB than HP is analagous to saying it's hot outside because the temperature is higher than the relative humidity. That's not what I meant, and an engineer ought to know that.

Maybe you're just a Microsoft Certified Systems Engineer. That would explain a lot.

Besides, I followed up the statement about "bias" with a couple of sentences explaining what I meant. In speaking of "bias," I compared the 4.6L 2V to the LS1. I still think my comparison with the LS1 is somewhat worthwhile. The 4.6L makes 1.162 FT/LB for every HP it makes. The LS1 makes only 1.098. The equation relating torque to power doesn't explain that. In fact, the opposite is true. That equation implies that motors with similar peak RPM numbers ought to have similar ratios of power to torque (and similarly shaped dyno curves). I guess I may be splitting hairs (and I know both motors are underrated by the OEM), but I'm not fundamentally wrong.

I also think you make a big mistake in trying to claim that the power/torque equation explains why "most cars become more responsive with higher RPM." Even if I accept your claim that responsiveness is the same as power, your statement is only true if a motor hits its power peak at the redline. Otherwise, there will be a region on the tachometer where power / responsiveness are decreasing with increasing RPM.

Besides, I don't agree that power equals responsiveness. Like I posted before, torque is twisting force. That's what you feel. That is what I meant by responsiveness. The car responds to throttle tip-in by shoving you in the back. Now, if you interpret "responsiveness" to mean "acceleration," I guess that peak power is more relevant to that than is peak torque. But even so, you can't claim that "most cars become more responsive with higher RPM." In fact, reality was almost the complete opposite during the late 1970s (whether you look at power or torque).

mogs01gt said:
4.6s have a very short stroke, that isnt that great for torque but it allows us to rev up higher and shift at a much higher RPM.

You'd better hope DBMSTANG doesn't read that one. If he does, he will almost have to tear you a new one or it will be obvious he has a personal problem with me.

Aaron 4.6 · Jun 1, 2004

Cudda- I would like you to respond to my thread instead of trying to win a pissing contest. I agreed with your premise, and I gave you an explanation. Instead of trying to show how big your capacity for argument is, you ought to be responding to my explanation of WHY you see WHAT it is that you see. I thought your intent was to have a little content in this post?

I also agree with you to disagree with mogs01gt. 3.55" isn't particularly short for piston stroke. The 2V 4.6 has 18% more stroke than a 302, and at stock redline the piston speed is about 40% greater for a 2V 4.6 than a stock 5.0 (5800 RPM/4800 RPM) * (3.55"/3.0") The square dimensions of the 4.6 represents a definite effort (to me at least) that Ford was trying to make up for the lost 21 c.i. by adding some torque via a longer stroke.

mogs01gt · Jun 1, 2004

why would he have a problem with that?

How is 3.55 not a short stroke? The 5.0s have a short stroke also. Both of these motors have a short stroke. This is why a lot of 302s(not only ford) have been able to rev up to 9k after modifications without problems. Im not sure if a SOHC motor could with the current aftermarket out there but its possible.

DBMSTNG · Jun 1, 2004

CuddaWuddaShuda said:
DBMSTANG: I get it. You interpret "bias toward torque" to mean that the FT/LB number is higher than the HP number. I can see where that interpretation would make me look dumb. But it's a stupid interpretation of the term "bias toward torque." It's an interpretation based on a comparison of two measurements despite the fact that they don't share the same units.

first of all, it's DBMSTNG.

are you John Kerry?

CuddaWuddaShuda said:
An engineer ought to know that comparing numbers with different units is not meaningful. Saying a motor has a torque bias because it has more FT/LB than HP is analagous to saying it's hot outside because the temperature is higher than the relative humidity. That's not what I meant, and an engineer ought to know that.

please, humor me. how pretell did you mean?

CuddaWuddaShuda said:
Maybe you're just a Microsoft Certified Systems Engineer. That would explain a lot.

or maybe i'm a manufacturing engineer for a company that does most of it's work for 3rd party autoindustry suppliers with mechanical design knowledge and know the fundamentals of engines.

CuddaWuddaShuda said:
Besides, I followed up the statement about "bias" with a couple of sentences explaining what I meant. In speaking of "bias," I compared the 4.6L 2V to the LS1. I still think my comparison with the LS1 is somewhat worthwhile. The 4.6L makes 1.162 FT/LB for every HP it makes. The LS1 makes only 1.098.

you do realize that once again, you contridict yourself. here you compare tq to hp. exactley what you claim you are not doing in the beginning of your post.

CuddaWuddaShuda said:
The equation relating torque to power doesn't explain that. In fact, the opposite is true. That equation implies that motors with similar peak RPM numbers ought to have similar ratios of power to torque (and similarly shaped dyno curves). I guess I may be splitting hairs (and I know both motors are underrated by the OEM), but I'm not fundamentally wrong.

you are wrong in that these 2 engines have next to nothing in common. one is a 4.6L ohc low compression engine and the other is a 5.7L pushrod with high compression. the 4.6L is underrated by about 10hp. the LS1 is underrated by as much as 45hp. and they will not have a similar ratio of tq/hp just because they have similar redlines. compression, heads, and cams all have a say in that.

CuddaWuddaShuda said:
I also think you make a big mistake in trying to claim that the power/torque equation explains why "most cars become more responsive with higher RPM."

OMG! torque is the actual power an engine produces. hp is a measurement of torque multiplied over time. just like gears, rpm multiplies torque. so the fastest acceleration in any gear will be at peak hp because that is when the amount of torque delivered over a given time is at it's most.

CuddaWuddaShuda said:
Besides, I don't agree that power equals responsiveness. Like I posted before, torque is twisting force. That's what you feel. That is what I meant by responsiveness.

as i mentioned earlier, go drive a S2000. it's peak torque is all over the place thanks to Vtec. but it doesn't push you back into the seat until after 6500rpm. why? because it's the multiplication of power.

CuddaWuddaShuda said:
But even so, you can't claim that "most cars become more responsive with higher RPM." In fact, reality was almost the complete opposite during the late 1970s (whether you look at power or torque).

those cars still accelerate fastest at peak hp. they produce their peak hp at a lower rpm than modern cars. it all relates back to the hp equation that you say you understand.

if you really insist, i'll keep informing you why you are incorrect and explaining why. but more and more, inside my head i hear "you cannot teach the willingly ignorant". you are wrong, just get over it. you are free to go educate yourself on the physics of the modern combustion engine.

DBMSTNG · Jun 1, 2004

and for the record, the stroke on the 4.6L isn't short, but it isn't long either. it's longer than a 302, but shorter than the LS1 and even the 2.3L in the Focus. <--EDIT just realized i confused the stroke of a 383 with the 346. the 4.6L has slighlty more stroke.

mogs is right about rpm vs stroke length.

short stroke = increased rpm capability

long stroke = more torque

DBMSTNG · Jun 1, 2004

here is a dyno of a near stock LS1. notice the torque curve is nowhere near that of the 2V. notice it makes almost 300hp AT THE REAR WHEELS. many times they produce OVER 300rwhp to the rear wheels stock.

http://www.ls1.com/link_dyno1.html

it makes close to peak torque at 5500rpm. the 4.6L does not. like i said before, this is a function of the compression, heads, and cams.

mogs01gt · Jun 2, 2004

My bolt on torque curve looked similar to that. I have a lot more torque drop off in the upper RPMs but that is do to our flowless stock heads and intake.

http://forums.stangnet.com/attachment.php?attachmentid=22783

and I still think the stroke on our cars AND the 302 are short. After helping build up a 454, then you realize how tiny these motors are.

97predator · Jun 2, 2004

the LS1 just makes silly power. i drove my friends with heads/cam/intake/lid/exhaust and could not believe it. it is not fair. to get that kind of power i would need a forged block and a kenne bell. approximately 8-9K to get where he is for 2-3K.

mogs01gt · Jun 2, 2004

97predator said:
the LS1 just makes silly power. i drove my friends with heads/cam/intake/lid/exhaust and could not believe it. it is not fair. to get that kind of power i would need a forged block and a kenne bell. approximately 8-9K to get where he is for 2-3K.

yeah but he bought a car with lower quality and all he got was an engine and at tranny.

CuddaWuddaShuda · Jun 2, 2004

DBMSTNG said:
are you John Kerry?

OK, that did sound a little like Kerry.

DBMSTNG said:
you do realize that once again, you contridict yourself. here you compare tq to hp. exactley what you claim you are not doing in the beginning of your post.

What I did was a little different from what you did. I made a ratio with different units on the top and bottom of the fraction, and then compared the ratios for two cars. That's an acceptable practice... think about "tons per cubic foot" as a way of comparing the density of substances.

What you did was a little different. You arbitrarily interpreted "torque bias" to mean FT/LB > HP and "power bias" to mean the reverse. Tons-per-cubic-foot is an acceptable measure of density, but if someone said a substance was lightweight because it weighed fewer tons than it spanned cubic feet, that would be very arbitrary.

DBMSTNG said:
you are wrong in that these 2 engines have next to nothing in common. one is a 4.6L ohc low compression engine and the other is a 5.7L pushrod with high compression. the 4.6L is underrated by about 10hp. the LS1 is underrated by as much as 45hp. and they will not have a similar ratio of tq/hp just because they have similar redlines. compression, heads, and cams all have a say in that.

My bad, next time I will post an exciting thread comparing nearly identical engines. We could compare the GM 231cid motor with the Ford 232cid motor. That might be enlightening.

Incidentally (and related to something you posted earlier), I am surprised that Chrysler copied the 4.6L. I don't usually find humor in corporate engineering decisions, but that 4.7L is good for a laugh. Gosh, I sure hope Chrysler puts out some cool 4.7L cars... stuff like the Continental or the Marauder.

Aaron 4.6 said:
Cudda- I would like you to respond to my thread instead of trying to win a pissing contest. I agreed with your premise, and I gave you an explanation. Instead of trying to show how big your capacity for argument is, you ought to be responding to my explanation of WHY you see WHAT it is that you see. I thought your intent was to have a little content in this post?

I also agree with you to disagree with mogs01gt. 3.55" isn't particularly short for piston stroke. The 2V 4.6 has 18% more stroke than a 302, and at stock redline the piston speed is about 40% greater for a 2V 4.6 than a stock 5.0 (5800 RPM/4800 RPM) * (3.55"/3.0") The square dimensions of the 4.6 represents a definite effort (to me at least) that Ford was trying to make up for the lost 21 c.i. by adding some torque via a longer stroke.

I agree with your original post. Your overall assesment (that the 4.6L is basically biased toward torque and is only "wild" compared to motors like the 302 and other late 70s / early 80s V8s) is probably true. My own seat-of-the-pants impressions are often incorrect. And I really don't want to own a torquer. I guess I do though; just another example of how I stumble through life. That's just because I wasn't raised right, though. (Now I sound like John Kerry again.)

As far as stroke goes, I consider the 4.6L to have a long stroke because its bore is barely larger than its stroke. That is pretty uncommon. I don't have the figures in front of me, but I bet the LS1 has a much bigger bore than stroke. Sure, if you compare a small block to a 454, the stroke looks short. I do like small blocks better than big blocks, and that is one reason.

I really didn't want to get into a pissing contest. If I had criticized a particular person or car, or made some kind of claim (as opposed to asking questions), I would have understood DBMSTNG's response. I think he is still upset about my Lightning thread. Trucks just ain't my thing. But that dude basically tried to make me look like an idiot in his first response, and I just couldn't let it slide. Hopefully everything is on the table now and we can be nice. I don't have any big issue with anything posted here (even DBMSTNG's technical arguments) but I do think that 1) some things I posted were (creatively) misinterpreted and 2) the tone was way out-of-line.

CuddaWuddaShuda · Jun 2, 2004

mogs01gt said:
yeah but he bought a car with lower quality and all he got was an engine and at tranny.

I know... it's almost like Chevy ran out of money and couldn't finish the car. I am thinking about things like skip-shift, the "hump" in the footwell, etc. Maybe I don't respect the 4.6L like I do the LS1, but the Ford wins the overall comparison between the two cars IMHO.

FallenPhoenix · Jun 2, 2004

CuddaWuddaShuda said:
I know... it's almost like Chevy ran out of money and couldn't finish the car. I am thinking about things like skip-shift, the "hump" in the footwell, etc. Maybe I don't respect the 4.6L like I do the LS1, but the Ford wins the overall comparison between the two cars IMHO.

That hump is just laziness or being cheap on the chassis IMO. That hump was on my '91 firebird and started in '82 with the third gen. A 20 year hump, could've been fixed in '93.

tooblue02 · Jun 2, 2004

This is how you fix the torque curve for a modular V-8

DBMSTNG · Jun 2, 2004

CuddaWuddaShuda said:
I really didn't want to get into a pissing contest. If I had criticized a particular person or car, or made some kind of claim (as opposed to asking questions), I would have understood DBMSTNG's response. I think he is still upset about my Lightning thread. Trucks just ain't my thing.

hardly upset over the lightning thread. it has rather commical. it was all centered on your notion that the Lightning sucked because it's top speed was 3mph slower than a GT. i pointed out that thread to show a pattern of your posts.

CuddaWuddaShuda said:
But that dude basically tried to make me look like an idiot in his first response, and I just couldn't let it slide.

i didn't make you look like anything, you did that all by yourself.

and you still have yet to mention what you ment by "torque biased".

2V Power Curve / Tradeoffs

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